My Dear Olivia,
I am so sorry that you are having to put up with her insensitivity. No one deserves this type of disrespect. You are not only responsible for naming your son but are responsible for his life. Obviously she doesn't realize that comments such as this carry a hurt that lasts a long time. I wish that you were my daughter-in-law (I have 2 and a son-in-law) there's always room in my heart for one more. My dear, I'll pray for peace for that place in your heart that she has hurt so much and for your family. This should be a time of great joy, not a time of hurt feelings and jealousy (I suspect she's having a bit of a fit).
Hugs and good wishes to you.